1. Field of the Invention
This invention relates to an improved apparatus and method for welding of metal plates and other objects that improves the fit between the objects and which decreases the deformation, movement or buckling of the welded items in the area surrounding the welded seam.
2. Prior Art
Presently, submerged arc welding is used in a variety of industries to weld one or more metal objects together, such as two metal plates. A welding shop may receive lengths of metal plate in rolled form and must unroll the metal plate using heat to flatten the plates as desired. The plates are then cut to desired dimensions using a plasma cutting machine or other suitable device.
When two metal plates are welded together, the adjacent ends of the two metal plates are laid next to each other on a welding bed to form a weld butt between the ends. The welding bed is simply that structure which supports the plates or other objects being welded together. In submerged arc welding it provides a space below the weld butt and usually comprises a series of magnets, also known as chucks, to secure each plate to the welding bed. The welding bed also usually comprises a length of non-ferrous, highly conductive material (referred to as a backing bar), often constructed from copper, that is positioned underneath the weld butt between the two adjacent ends of the two metal plates. A copper backing bar is considered non-consumable because it will not be integrated into the material being welded together because the melting temperature of copper is higher than that of the (usually) steel plates. However, a consumable backing bar, typically made of iron or steel, may be used as well where it is desired to weld the backing material to the other objects being welded together. Finally, when welding methods other than the submerged arc method are used, the backing bar may not be used at all.
Conductive welding flux is placed on top of the backing bar before the plates are in position and poured between the two adjacent ends until it substantially fills the weld butt between them. The flux controls the atmosphere around the weld, preventing oxygen and other foreign material which may weaken the weld from contacting the weld.
A submerged arc-welding machine, having a source of electric current, passes along the weld butt between ends of the metal plates, and the flux allows the electric current to pass between the ends of the plates. The electric current heats the metal to at least its melting point and melts the ends of the plates. The current also melts a filler wire or rod which is positioned over the weld butt. The melted filler and the melted ends of the plates or other objects pool to form a common weld puddle. As the puddle cools and hardens, a welded seam is formed between the plates.
Unfortunately, present methods have disadvantages. The metal plates, and/or then ends thereof, have a tendency to move and buckle along the seam during welding because the heat involved causes the metal to expand. In some instances, the buckling and movement of the metal plates results in broken and uneven weld seams and uneven plate surfaces before the welded seam solidifiesxe2x80x94undesirable results in a welding process.
Although magnets are used to secure the metal plates to a welding bed, positioning the magnets too close to the welded seam is undesirable because the magnets affect the weld puddle, or molten metal that cools to form the welded seam. The magnets may xe2x80x9cpullxe2x80x9d the weld puddle away from the weld butt area where the welded seam is formed, resulting in a weakened welded seam. Thus in the area where the displacement forces from the heat will be the most intense, there is nothing holding the plates in place.
The present invention provides an advantage over prior art apparatuses and methods. By using a device that applies pressure to the metal plate or plates adjacent to the welded seam, the present invention decreases the movement and buckling of the metal plates that is normally associated with prior art apparatuses and methods. Because pressure is applied along the weld butt between the plates and along the welded seam until the welded seam sufficiently solidifies, the present device ensures that the welded seam and/or the metal plate area surrounding the welded seam will not deform, buckle, or significantly distort.
With the aforementioned considerations in mind, it is therefore an object of this invention to provide an improved welding apparatus that minimizes movement, deformation, and buckling of metal plates during the welding process.
It is a further object of the present invention to provide an improved welding process that minimizes movement, deformation and buckling of metal plates during the welding process.
It is a further object of the present invention to provide an apparatus that may connect to or cooperate with an existing submerged arc or other welding apparatus to apply pressure to the area surrounding a welded seam until that welded scam sufficiently solidifies.
It is a further object of the present invention to fit plates or other objects together for welding.
These and other advantages and objects of this invention shall become apparent from the ensuing description of the invention.
This invention comprises a process and an apparatus for applying pressure to metal plate or plates during a welding process. The pressure applicator apparatus may be constructed as part of a welding apparatus or constructed separately and used in conjunction with an existing welding apparatus.
The pressure applicator apparatus may comprise a first pressure applicator configured to contact at least a portion of a first plate adjacent to a weld butt and/or the welded seam between two plates being welded together and a second pressure applicator configured to contact at least a portion of a second plate adjacent to the weld butt and/or the welded seam. The pressure applicators are configured to apply pressure to the plates near the weld butt or the welded seam until the welded seam formed between the plates has sufficiently cooled and hardened to resist significant distortion of the plates.
When constructed as part of a welding apparatus, the invention may comprise (a) a welding bed configured to support one or more metal plates having upper and lower surfaces and ends in an end-to-end relationship with a weld butt between the ends; (b) a source of electric current positioned sufficiently near the bed to allow the current to pass from the current source to the plates, whereby a welded seam may be formed between the plates; the source of electric current or welding bed is configured to move the current source in a path that substantially follows the weld butt between the ends of the plate or plates; and (c) at least one pressure applicator positioned on each side of the weld butt and positioned to contact the plate at a position adjacent to the ends of the plate; the pressure applicators are preferably configured to extend from a point before the source of electric current to a point behind the source of electric current, relative to the direction of movement of the source of electric current or of the movement of the plates, whereby pressure may be applied to the plates for a sufficient period of time to allow the weld seam to solidify sufficiently to resist displacement.
The methods of the present invention can be used when welding flat or curved (concave or convex) metal plates or other metal objects, such as pipe. The method prevents movement, deformation, buckling or substantial distortion of metal plates during a welding process wherein two metal plates are welded together using a source of electric current that forms a welded seam between the metal plates. In general, the improved method comprises the steps of applying pressure to the metal plates along the welded seam to prevent the welded seam from being significantly distorted, moved, deformed or buckled while the welded seam sufficiently solidifies.
In particular, the method may comprise the steps of (a) providing at least two metal plates having upper and lower surfaces and ends; (b) positioning the plates end-to-end on a welding bed; (c) arcing electric current from a source of electric current to plates, thereby melting the ends and creating a welded seam between the plates; (e) applying pressure to the upper surface of the plates with at cast one pressure applicator positioned on each side of the weld butt and/or welded seam between the plates and configured to extend sufficiently behind the source of electric current to allow the pressure applicators to apply sufficient pressure to the plates to prevent the welded seam from being significantly distorted, moved, buckled or deformed while the welded seam solidifies; and (f) moving the plates or the current source so that the current source arcs electric current through and along the weld butt.